1. Field of the Invention
The invention relates in general to an apparatus for accessing a recording medium and a method for recovering medium management information, and more particularly to a write-once optical disc drive and a method for recovering disc management information.
2. Description of the Related Art
Recording media of high-density data storage, such as optical discs, are developing for storing much more data in order to meet the needs of storing large amount of multimedia data with smaller number of recording media. The optical discs, such as blu-ray discs, provide capacity of up to tens of GBs. With such large capacity for data storage, disc management indicating the status of the optical disc ensures error free storage space and enables different recording modes. A recording medium generally provides areas for storing information for disc management and reading or writing user data on the recording medium requires accessing the latest disc management information. Once the disc management information becomes unreliable, such as being damaged, lost, or out-of-dated, the user data being read from or written into the recording medium would be unreliable. In such case, the disc management information must be recovered before further accessing of the recording medium.
As an example, before a recordable blu-ray disc (BD-R) is closed or finalized, a data structure called temporary disc management structure (TDMS) is employed for disc management. The BD-R supports two recording modes, sequential recording mode (SRM) and random recording mode (RRM), and recording data on a BD-R can only be performed under a selected one of the two recording modes. The TDMS for a BD-R includes disc management information, depending on the recording mode selected for the BD-R. For SRM, the TDMS includes a temporary disc definition structure (TDDS), a temporary defect list (TDFL), and sequential recording range information (SRRI). For RRM, the TDMS includes a TDDS, a TDFL, and a space bit map (SBM). In order to indicate whether the information contained in the TDDS is reliable, a number of specific fields, called inconsistency flags in BD-R specifications, as in FIG. 2, are defined in the TDDS for either SRM or RRM. When one of the inconsistency flags is set to a value, such as 1, indicating that a disc is in the drive for accessing the disc and the information associated with this flag in the TDMS may not be reflecting the actual status of the disc, the information associated with this flag is unreliable and must be recovered.
However, the conventional approaches to recovery of information associated with an inconsistency flag are inefficient. According to the BD-R specifications section 6.7.6.4, a method for rebuilding the TDFL has been described involving reading all the replacement clusters when the TDFL is damaged or invalid due to e.g. power failure. Regarding SBM or LRA, rebuilding requires reading all clusters of the disc conventionally. All these methods are time-consuming and thus inefficient.
Therefore, it is desirable to recover the information of the TDMS efficiently in a case that the information for disc management is unreliable.